The present invention is generally directed to molds used in injection molding machines, and is more specifically directed to a mold having cavities adapted to receive and retain mold inserts.
Molds used in injection molding machines generally include mold halves or sections which include portions that define the features of the items being molded. Since injection molding machines involve high temperatures and pressures, as well as mechanisms for cooling and ejecting molded components, the actual portion of the mold that defines the shape of the final product to be molded comprises only a small part of the entire mold assembly. As such it is beneficial to provide interchangeable mold modules that comprise that portion of the mold that defines the final molded product while maintaining a module support frame common to any number of these modules.
As such, molds used in the injection molding process often include a frame having one or more cavities therein each adapted to accept a mold module for producing the same or different molded parts. In general these mold modules are bolted in place and must be unbolted to remove the module from the mold. This is often time consuming and inconvenient as tools must be on hand to at least partially disassemble the mold. In addition, the bolts can be difficult to remove; sometimes resulting in stripped threads in the mold as well as in broken bolts. Moreover if a module must be changed quickly, the mold and module may be extremely hot further exacerbating the problem of mold removal.
Based on the foregoing, it is the general object of the present invention to provide a mold assembly that overcomes the problems associated with prior art molds.
The present invention is directed in one aspect to a modular mold assembly comprising first and second mold frame halves, each defining at least one aperture extending therethrough. When the mold halves are assembled, these apertures cooperate to define a mold cavity. A mold module having a surface defining at least in part a portion of the item to be molded, is slidingly receivable in each of the apertures defined by the first and second mold frame halves. Once the mold modules are positioned within the apertures, locking means are employed to secure each mold module within its respective aperture in response to the first and second mold frame halves being brought into engagement with one another. The locking means also acts to release each mold module from a respective one of the first and second mold frame halves is response to the first and second mold frame halves being separated from one another.
In the preferred embodiment of the present invention, the locking means includes a first and second locking wedge; each with first locking wedges being coupled of the first and second mold frame halves and positioned in each apertures. The second locking wedges are slidingly coupled to the first locking wedges and are movable between a locked position wherein an outwardly facing surface defined by the second locking wedges thereby engages and securedly retains the mold module positioned in one of the mold frame half apertures, and an unlocked position wherein the outwardly facing surface is spaced away from the mold module, making the mold module freely removable from the respective first or second mold frame half.
In the preferred embodiment of the present invention, the first locking wedges each define a tapered surface slidingly engaged with a respective one of the second locking wedges. Accordingly, as the first and second mold frame halves are brought into engagement with one another, the tapered surface of the first locking wedges progressively engages the second locking wedge causing the outwardly facing surface to engage the mold module releasably retaining it within the mold cavity. Conversely, upon separation of the first and second mold frame halves, the tapered surface of the first locking wedges progressively disengages the second locking wedge causing the outwardly facing surface to move away from the mold module thereby allowing it to be freely removable from the aperture in either the first or second mold frame halves.
Preferably, a respective one of each of the second locking wedge and lacking wedges defines a dovetail-shaped groove with the other defining an outwardly projecting dovetail-shaped protrusion adapted to mate with the groove. It is also preferable that the surface of the second locking wedge engageable with the first locking wedge also be tapered. In this manner, small movements of the first locking wedge relative to the second locking wedge causes larger concomitant movement of the outwardly facing surface of the second locking wedge toward or away from the mold module.
The preferred embodiment of the present invention also includes a mold frame base upon which are positioned the first and second mold frame halves, one-on-top-of-the-other. A series of springs are positioned between the mold frame halves for urging the halves away from one another. During a molding operation the mold frame halves are pressed together and retained in that position be one or more clamps movable between a locked and unlocked position.
A mounting plate is coupled to the mold modules positioned within the apertures in the mold frame halves. A mounting member projects outwardly from the mounting plate and is adapted to frictionally engage a bushing positioned in an aperture defined by the mold frame base. The frictional force exerted between the mounting member and the bushing is sufficient to hold the mounting modules in place when the mold frame halves are separated to eject the molded items from the mold modules. The frictional force is not sufficient to overcome the force exerted by the springs, thereby allowing the first and second mold frame halves to separate when the clamp is released.
Preferably, the mounting member is in the form of a polymeric bushing threadedly attached to the mounting plate via a fastener. The polymeric bushing includes a tapered bore extending longitudinally therethrough and the fastener defines a tapered peripheral surface adapted to mate with the tapered bore so that subsequent tightening of the fastener causes an outer periphery defined by the polymeric bushing to expand, thereby providing the capability to set the desired amount of friction between the bushing in the mold frame base and the polymeric bushing. While a polymeric bushing has been described, the present invention is not limited in this regard as other materials such as metals or elastomers can be substituted without departing from the broader aspects of the present invention.